The present invention relates to a laminated film, a method for the production thereof, a bag and a package both using the laminated film, and a method of the peeling (or separating) thereof.
Heretofore, for the purpose of accommodating agricultural chemicals and other various commodities, bags which are made of a laminated film having the component layers thereof joined by lamination so strongly as to be impossible to peel have been used. The conventional laminated film has for the innermost layer thereof a film (such as, for example, LLD-PE (linear low-density polyethylene) film) that is thermally adhesive (namely heat-sealable) to itself. A commodity is placed in a hermetically sealed bag produced by superposing this laminated film so that the thermally adhesive film is positioned inside, and heat-sealing the prescribed portions of the superposed laminated film so that the parts of the thermally adhesive film facing to each other at the prescribed portions are fused to each other.
As means for enabling commodities to be contained in hermetically sealed bags that are made of the laminated film mentioned above, the two methods called "bag supplying method" and "automatic packaging method" are known. The bag supplying method comprises a manufacturer of bags initially producing bags open in one side from the laminate film mentioned above and a manufacturer of commodities then receiving the supply of these bags, filling the bags with their commodities via the openings thereof, and thereafter occluding the openings of the bags by heat-sealing. The automatic packaging method comprises a manufacturer, for example, of commodities forwarding the laminated film mentioned above through the sequential steps of the process of production of bags such as, for example, superposing the laminated film upon itself, heat-sealing the prescribed portions of the superposed laminated film, and filling the formed bags with their commodities, and finally obtaining hermetically sealed bags accommodating the commodities therein. Irrespectively of the choice between these two methods, automatic machines adapted to automate the steps of manufacture mentioned above have been finding extensive adoption by the manufacturers of commodities. In the case of the bag supplying method, for example, such automatic machines as are capable of automatically filling the bags opened in one side with the commodities and then automatically heat-sealing the openings of the filled bags are used. In the case of the automatic packaging method, such automatic machines as are capable of automating the process of automatic packaging mentioned above are used.
Generally, even when the commodity to be contained happens to be a powdery agricultural chemicals (which is generally diluted with water prior to use), for example, it is directly contained in the bag that is made of the conventional laminated film mentioned above. When a user of the agricultural chemicals opens the bag, the powdery agricultural chemicals is drifted up through the opened side of the bag possibly to be inhaled by the user or suffered to impinge on the user's hands, with the result that the powder will do harm to the user's system. When the user transfers the powdery agricultural chemicals from the bag into a tank for the purpose of diluting it with water, the powdery agricultural chemicals is likewise drifted up and suffered to do harm to the user's system. Even after the agricultural chemicals has been extracted from the bag, the remnant thereof adheres to the inner wall of the bag. If the bag in this condition is discarded among the household rubbish, therefore, it will form a cause for environmental pollution.
For the purpose of safeguarding the environment against this danger, therefore, the practice of containing a given powdery agricultural chemicals in a bag made of a water-soluble film, hermetically sealing this bag, further containing the bag of the water-soluble film accommodating the agricultural chemicals in a bag formed of the conventional laminated film mentioned above, and hermetically sealing the outer bag has been in vogue in recent years. In this case, the bag of the water-soluble film serves as an inner bag and the bag of the conventional laminated film as an outer bag. The reason for using the outer bag in this manner is that the water-soluble film succumbs readily to the degeneration by the ambient condition and possesses no sufficient strength.
When the inner bag and the outer bag are used as described above, the outer bag can be opened without entailing the danger of drifting up the agricultural chemicals and the inner bag containing the agricultural chemicals can be directly placed in a tank and diluted with the water accommodated in the tank (because the inner bag of the water-soluble film dissolves on contact with water), with the result that the composite bag will ensure perfect ease of handling because the agricultural chemicals accommodated therein no longer has the possibility of doing harm to the user's system or jeopardizing the safety of the environment. After the agricultural chemicals has been extracted from the outer bag, absolutely no remnant thereof is adhering to the inner wall of the outer bag. When the outer bag is discarded as it is among household rubbish, therefore, it entails absolutely no problem.
The foregoing remarks hold good not only for the powdery agricultural chemicals mentioned above but also for a granular or liquid agricultural chemicals and other various commodities.
The conventional practice of using both an inner bag and an outer bag, however, incurs a huge cost. This conventional practice of using both an inner bag and an outer bag, for example, requires inner bags to be separately produced and necessitates an extra cost for this production. The operation of placing the inner bag accommodating a given commodity in the outer bag, for example, necessitates the use of new devices at an extra cost of equipment because this operation does not permit use of the aforementioned existing automatic machines which fit the bag supplying method and the automatic packaging method mentioned above.
The idea of preparing a laminated film having an outer-layer-film and a water-soluble film weakly joined to each other in a peelable manner through the adhesive of weak adhesive force (adhesive strength or peel strength) and, in accordance with the conventional bag supplying method or automatic packaging method mentioned above, superposing this laminated film so that the water-soluble film is positioned inside, heat-scaling the prescribed portions of the superposed laminated film so that the parts of the water-soluble film facing to each other a the prescribed portions are fused to each other, thereby forming a hermetically sealed bag, and containing a commodity in this bag is conceivable in the circumstance. Incidentally, the water-soluble film is generally thermally adhesive to itself.
According to this method employing the adhesive, the bag made of the laminated film mentioned above has a double-wall structure consisting of an outer-layer-film functioning as an outer bag and a water-soluble film functioning as an inner bag. The user of the commodity contained in this bag, similarly to the aforementioned composite bag consisting of an inner bag and an outer bag, is only required to peel (or separate) the outer-layer-film to obtain the commodity as contained in the inner bag of the water-soluble film without entailing the danger of drifting up the commodity such as, for example, agricultural chemicals. He is then required to place the inner bag still accommodating the commodity in the tank and dilute it with the water accommodated in the tank (because the bag made of the water-soluble film dissolves on contact with water), with the result that the user will enjoy perfect ease of handling because the commodity accommodated therein no longer has the possibility of doing harm to his system or jeopardizing the safety of the environment.
Since the laminated film mentioned above can be handled during the insertion of a given commodity therein in the same manner as the conventional laminated film, the existing automatic machines and other devices can be used in their unmodified form. The bag incurs no noticeable addition to the cost of production because it obviates the necessity of separately producing inner bags unlike the aforementioned composite bag consisting of an inner bag and an outer bag.
In the method resorting to an adhesive agent, the adhesive agent is not easily obtained as vested with ideal properties for the adhesion contemplated by the method. The product of this method, therefore, has the possibility that the properties of the adhesive and the water-soluble film will vary with the elapse of time because of the reaction between the components of the adhesive and the water-soluble film. The possibility that the outer-layer-film will not be easily peeled off from water-soluble film when the user seeks to use the commodity accommodated in the bag, the outer-layer-film will peel from the water-soluble film before the bag reaches the user, the water-soluble film will sustain pinholes therein, or the water-soluble film will suffer degradation of the water-solubility thereof, therefore, is undeniable. Further, the possibility exists that part of the adhesive will remain on the water-soluble film and go to impair the solubility of the water-soluble film after the outer-layer-film has been peeled from the water-soluble film and the components of the adhesive will react with the components of the commodity such as, for example, agricultural chemicals in the tank accommodating water and degenerate the commodity after the water-soluble film has been dissolved in the water during the use of the commodity.
In the method described above, the user of the commodity accommodated in the bag incurs inconvenience in peeling the outer-layer-film unless the bag is provided with a part which becomes a beginning for peeling the outer-layer-film.